Treasurer Scott Morrison has said income inequality is not getting worse in Australia.
Photograph: Brendan Esposito/AAP

Australia is among countries with the highest growth in income inequality in the world over the past 30 years, according to the International Monetary Fund.

Vitor Gaspar, the IMF’s director of fiscal affairs, has told an audience at the launch of the IMF’s latest Fiscal Monitor that Australia’s income inequality growth has been similar to the US, South Africa, India, China, Spain and the UK since the 1980s.

Gaspar said IMF staff had used the Organisation for Economic Co-operation and Development’s income distribution database, Eurostat, and the World Bank’s Povcalnet data, among other sources, to calculate that income inequality had increased in nearly half of the world’s countries in the past three decades, and Australia had experienced a “large increase” in that time.

“Most people around the world live in countries where inequality has increased,” he said.

The IMF’s latest Fiscal Monitor, released overnight, is dedicated to the global growth in income inequality. It warns that while some inequality is inevitable in a market-based economic system as a result of “differences in talent, effort, and luck”, excessive inequality could “erode social cohesion, lead to political polarisation, and ultimately lower economic growth”.

It also warns that income inequality tends to be “highly correlated” with wealth inequality, inequality of opportunity, and gender inequality.

“The latest census showed on the global measure of inequality, which is the Gini coefficient, that is the accepted global measure of income inequality around the world and that figure shows it hasn’t got worse, it has actually got better,” he said.

He was technically right – if you only consider the last few years.

The Gini index is the most widely used measure of inequality. It looks at the distribution of a nation’s income or wealth, where 0 represents complete equality and 100 total inequality.

The 2016 census showed the Gini coefficient for equivalised disposable household income in Australia fell from 0.333 in 2013-14, to 0.323 in 2015-16.

Morrison did not mention that the Gini coefficient had been even lower in 2005-06, at 0.314.

“Wealth inequality has become more pronounced particularly in the last five or six years because there’s been big gains in asset prices,” Lowe said. “So the people who own assets, which are usually wealthy people, have seen their wealth go up.”

He said income inequality had increased slightly in recent years, but wealth inequality was more pronounced because of rising asset prices.